Mammals have two kidneys, one on each side in the region of the mid to lower back. Each kidney is composed of about 1 million nephrons. A nephron is composed of a renal corpuscle and a renal tubule specialized for re-absorption and excretion.
Renal disease results from damage to the nephrons, causing them to not function properly. Renal failure can be divided into acute (a rapid onset) or chronic (slowly progressive over time).
Depending on the causes, a number of different diseases (e.g., glomerulonephritis or diabetic neuropathy associated with diabetic or hypertensive complications) can result in renal disease. It may be the direct result of an infection or a drug toxic to the kidneys.
Chronic renal failure is defined as either kidney damage or glomerular filtration rate of less than 50%. Irrespective of the initiating insult, this is invariably a progressive process that results in end-stage renal disease (ESRD). Over the years, ESRD may be a life-threatening disease caused by other complications in blood, nerve system, gastrointestinal system, and immune system as well as by infection or osteodystrophy.
The number of patients with renal disease is growing worldwide, but symptoms are often not apparent until renal failure is advanced. In Korea, there are about 450,000 people with renal failure and a total of patients including early-diagnosed ones are likely to further increase.
After ESRD occurs, renal replacement therapy is required, in the form of either dialysis or transplant. However, its wide use is restricted due to failure in treating the underlying cause of chronic renal failure in early and middle stage, and higher medical costs that are burdensome to patients and their family members.
Recently, many researchers at home and abroad have made intensive studies on the mechanism of impaired renal functions and as a result, some compounds with simple chemical structures have been made available as a means of controlling blood pressure and treating the original disease, whenever feasible. For instance, angiotensin converting enzyme (ACE) inhibitors are used, as they have been found to slow the progression to ESRD. Replacement of erythropoiesis stimulating factor (ESF) and activated vitamin D3, two hormones processed by the kidney, is usually necessary. Nevertheless, the wide use of these drugs has been quite restricted due to higher drug costs and palliative therapy. In this context, there is urgent need for the development of novel drugs for treatment of renal disease in the pharmaceutical sector.
Recent drug development has focused on chemical platforms that have been derived from natural sources. With a combination of novel properties, structure and less toxicity, natural products today are most likely going to continue to exist and grow to become even more valuable as sources of new drug leads.
In keeping abreast of the current trends of drug development, the inventors have tested a number of herb medicines to ensure that they are effective for improving the renal function in patients with renal failure.
Puerariae Radix, which belongs to Leguminosae, a root in which the periderm of Pueraria thunbergiana is removed. This plant has been shown to possess lipid lowering (Modern Chinese Medicines and Clinical Application, 626-632, 1994) and anti-diabetic properties (Anti-senility Chinese Medicine and Pharmacology, 186-187, 1989).
Bombycis corpus, a batryticated silkworm and white-stiff silkworm, is a drug consisting of the dried larva of silkworm, Bombyx mori, dead and stiffened due to the infection of Beauveria. This natural product has been also shown to exhibit anti-diabetic action (Journal of the Korean Society for Hygienic Science, Vol. 6, No. 1, 2, 11-33 (2000)) with lipoprotein as an active ingredient.
Araliae Continentalis Radix, which belongs to Araliaceae, is a root of Araliae Continentalis. This natural product is pungent, bitter and soft in its nature and has a combination of properties such as tonics, anti-inflammatory and lipid lowering actions (Korean J. of Pharmacognosy, 24 (3), 219-222 (1993)). Araliae Continentalis Radix contains angelol B, nerolidol, ostehnol, osthol, Isoimperatorin, ferulin, and oleanolic acid.
The inventors have endeavored to screen a wide variety of promising herb medicines and health foods listed in the Korean Food Standard Code to find a potential for prevention and treatment of renal disease. As a consequence the inventors have discovered that Puerariae Radix, Bombycis corpus and Araliae Continentalis Radix may be useful for the improvement of renal functions and consummated this invention.